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Transcript of Outernet Main report
ABSTRACT
THE OUTERNET
There are more computing devices in the world than people, yet less than 40% of the global
population has access to the wealth of knowledge found on the Internet. The price of smart
phones and tablets is dropping year after year, but the price of data in many parts of the world
continues to be unaffordable for the majority of global citizens. In some places, such as rural
areas and remote regions, cell towers and Internet cables simply don't exist. The primary
objective of the Outernet is to bridge the global information divide.
Access to knowledge and information is a human right and Outernet will guarantee this right by
taking a practical approach to information delivery. By transmitting digital content to mobile
devices, simple antennae, and existing satellite dishes, a basic level of news, information,
education, and entertainment will be available to all of humanity. Although Outernet's near-term
goal is to provide the entire world with broadcast data, the long-term vision includes the addition
of two-way Internet access for everyone. For free.
Outernet consists of a constellation of low-cost, miniature satellites known as ‘Cubesats’ in Low
Earth Orbit. Each satellite receives data streams from a network of ground stations and transmits
that data in a continuous loop until new content is received. In order to serve the widest possible
audience, the entire constellation utilizes globally-accepted, standards-based protocols, such as
DVB(Digital Video Broadcasting), Digital Radio Mondiale, and UDP-based WiFi multicasting.
RAJANISH KUMAWAT
Enroll no.- 10E1SOECM3XT092
1
Chapter-1
INTRODUCTION
1.1 Outernet: The Outernet is a global networking project currently under development by
the Media Development Investment Fund (MDIF), a United States-based non-profit
organization established in 1995. The Outernet's goal is to provide free access to internet data
through wifi, made available effectively to all parts of the world.
The project would involve using datacasting and User Datagram Protocol through hundreds
of CubeSats measuring 10 cm (3.9 in) each. Wi-fi enabled devices would communicate with the
satellites in their region, which in-turn communicate with other satellites and ground-based
networks, thus forming the global network.
The network would initially support only one-way traffic, with two-way traffic being
implemented once adequate funding is raised. Initial prototype satellite deployments is planned
for June 2014, with the final deployment run scheduled for mid-2015. According to MDIF, the
initial content access includes international and local news, crop prices for farmers, Teachers
Without Borders, emergency communications such as disaster relief, applications and content
such as Ubuntu, movies, music games, and Wikipedia in its entirety.
MDIF plans to formally request NASA to use the International Space Station to test their
technology in September 2014. Manufacturing and launching of satellites would begin in early
2015, and Outernet is planned to begin broadcasting in June 2015. India based "Spacify Inc." is a
private non-profit company by Silicon Valley based technocrat and entrepreneur Siddharth
Rajhans along with Space debris mitigation expert Sourabh Kaushal, which is privately working
on using this technology to provide global free wi-fi access.
2
A small team of workers at a New York based non-profit organization called Media
Development Investment Fund (MDIF) has announced its intention to build an "Outernet"—a
global network of cube satellites broadcasting Internet data to virtually any person on the planet
—for free. The idea, the MDIF website says, is to offer free Internet access to all people,
regardless of location, bypassing filtering or other means of censorship.
As the Internet has grown in size and importance, human rights organizations, or those (such as
MDIF) promoting freedom of expression, have begun to propose that access to the information
that the Internet can provide, is a basic human right. Conversely, they suggest that restricting
access to the Internet is a violation of human rights. MDIF seeks to circumvent those that might
wish to violate such human rights by bypassing their ability to restrict access—they are
proposing that hundreds of cube satellites be built and launched to create a constellation of sorts
in the sky, allowing anyone with a phone or computer to access Internet data sent to the satellites
by several hundred ground stations.
MDIF claims that 40 percent of the people in the world today are still not able to connect to the
Internet—and it's not just because of restrictive governments such as North Korea—it's also due
to the high cost of bringing service to remote areas. An Outernet would allow people from
Siberia to parts of the western United States to remote islands or villages in Africa to receive the
same news as those in New York, Tokyo, Moscow or Islamabad. That they say, would guarantee
all people the same Internet rights as everyone else.
The Outernet, as envisioned, would be one-way—data would flow from feeders to the satellites
which would broadcast to all below. MDIF plans to add the ability to transmit from anywhere as
well as soon as funds become available. At this time, it's not clear how much MDIF has been
able to collect for the project, but acknowledge that building such a network would not be cheap.
Such satellites typically run $100,000 to $300,000 to build and launch. Still, the timeline for the
project calls for deploying the initial cubesats as early as next summer.
3
Figure1(a):- Outernet Plan or Idea
1.2 Need of Outernet: There are more computing devices in the world than people, yet less than
40% of the global population has access to the wealth of knowledge found on the Internet. The
price of smartphones and tablets is dropping year after year, but the price of data in many parts
of the world continues to be unaffordable for the majority of global citizens. In some places, such
as rural areas and remote regions, cell towers and Internet cables simply don't exist. The primary
objective of the Outernet is to bridge the global information divide.
Broadcasting data allows citizens to reduce their reliance on costly Internet data plans in places
where monthly fees are too expensive for average citizens. And offering continuously updated
web content from space bypasses censorship of the Internet. An additional benefit of a
unidirectional information network is the creation of a global notification system during
emergencies and natural disasters.
Access to knowledge and information is a human right and Outernet will guarantee this right by
taking a practical approach to information delivery. By transmitting digital content to mobile
4
devices, simple antennae, and existing satellite dishes, a basic level of news, information,
education, and entertainment will be available to all of humanity.
Although Outernet's near-term goal is to provide the entire world with broadcast data, the long-
term vision includes the addition of two-way Internet access for everyone. For free.
Satellites need to be controlled from earth to fully utilize their functionality. To do this optimally
satellites need the longest and most frequent possible communication access times with their
groundstations. Large satellites currently use services such as NASA’s Tracking and Data
Relay(TDRS), and distributed ground station networks such as SSC’s PrioraNet. These services
are however very expensive and not available for commercial use. The launch of micro-, nano-
and pico-satellites are rapidly increasing among smaller companies and universities. The use of
above mentioned TT&C services are not economically feasible for these smaller satellite
missions. The only option left for these projects is to build and maintain a small ground station
which can amount up to a third of the total mission budget.
1.3 Mission Objectives: To address this shortfall the following mission objectives are set:
- Provide a communication opportunity to any satellite in Low Earth Orbit (LEO) at least once
each orbit.
- Provide this service to worst-case communication link budget client, namely a 1U CubeSat
with VHF/UHF monopole
- The service should be cheaper to use than constructing and maintaining a small ground station
over the mission lifetime
5
Chapter-2
HOW IT WORKS
2.1 How Does It Work: Outernet consists of a constellation of low-cost, miniature satellites in
Low Earth Orbit. Each satellite receives data streams from a network of ground stations and
transmits that data in a continuous loop until new content is received. In order to serve the widest
possible audience, the entire constellation utilizes globally-accepted, standards-based protocols,
such as DVB, Digital Radio Mondiale, and UDP-based WiFi multicasting.
Citizens from all over the world, through SMS and feature-phone apps, participate in building
the information priority list. Users of Outernet's website also make suggestions for content to
broadcast; lack of an Internet connection should not prevent anyone from learning about current
events, trending topics, and innovative ideas.
2.2 The project consists of three segments:
1. The Space Segment
2. The Ground Segment and
3. The User Segment.
The space segment (OuterNet) consists of 14 satellites evenly spaced in a 900km circular
equatorial orbit. The constellation’s beam width coverage is such that all LEO satellites in orbits
below 600km altitude will come into range of the constellation at least once every orbit (refer to
orbit/constellation design for details). When within range, the client satellites can be polled by
the constellation to download telemetry and/or upload tele-commands.
6
Figure 2(a): Conceptual Illustration of the OuterNet
The ground segment consists of several ground stations spread around the equator. Due to the
constellation’s equatorial orbit, each of the satellites will pass every ground station during every
orbit. Three potential ground stations have already been identified: Guiana Space Centre, Broglio
Space Centre and Pusat Remote Sensing.
The user segment consists of clients who register to use the OuterNet service. Pricing will be
based on the amount and frequency of data relayed. Satellite operators will be able to configure
their TT&C schedules, download telemetry, upload telecommands and configure their
communications protocol and modulation technique through a user friendly internet interface.
7
Figure 2(b): Interfacing between system segments
Broadcasting data allows citizens to reduce their reliance on costly Internet data plans in places
where monthly fees are too expensive for average citizens. And offering continuously updated
web content from space bypasses censorship of the Internet. An additional benefit of a
unidirectional information network is the creation of a global notification system during
emergencies and natural disasters.
Access to knowledge and information is a human right and Outernet will guarantee this right by
taking a practical approach to information delivery. By transmitting digital content to mobile
devices, simple antennae, and existing satellite dishes, a basic level of news, information,
education, and entertainment will be available to all of humanity.
2.3 Key Performance Parameters: The key performance parameters for the proposed mission
are:
(a) Communication latency
(b) Communication Power
(c) Data Capacity
(d) Target Orbit
8
2.3.1 Communication latency: The time it takes for the client satellite to move into range of the
constellation communication footprint. It is dependent on the footprint width on the orbit of the
client satellite, which is in turn dependent on the antenna system and number of satellites in the
constellation. A target intersection occurrence is once per client satellite orbit.
2.3.2Communication power: The system must work even if the client satellite has limited
communication power. Worst-case client for this parameter is defined as a standard 1-U
CubeSat.
2.3.3 Data capacity: Data transferred during a single target intersection occurrence depends on
the mean intersection duration and the data rate. The duration depends on the width/area of the
communication footprint, which in turn is dependent on the antenna system beam width. A
transfer rate of 4800bps will allow for a telemetry packet of about 35kb given a 60-second
communication window.
2.3.4 Target orbits: The constellation must supply this service to satellites in orbits ranging
from 300km to 800km altitude.
Figure 2(c): Antenna coverage on different orbits
9
2.4 Orbit/Constellation Description: The orbit design of the system consists of calculating the
orbital parameters (inclination, eccentricity and semi-major axis) and determining the amount of
satellites needed for the constellation. An equatorial orbit is chosen to ensure that the satellites
will pass a ground station, which will be situated as close as possible to the equator, at least once
per orbit. Any other orbit would cause the satellite to drift away from the ground station because
of the rotation of the earth. The long latency between communication opportunities between
satellites in more inclined orbits (e.g. polar and sun-synchronous) and their ground stations is the
problem that our system will improve upon. With the proposed system, client satellites will cross
our constellation twice per orbit. There exist areas, at different altitudes, where satellites can slip
through without being able to communicate with the constellation. These areas are illustrated in
Figure 3. However, client satellites would never pass through these areas more than once per
orbit, ensuring communication at least once per orbit. A passing client satellite will have access
time to a satellite in the constellation, which depends on the area of the antenna’s beam on the
orbital plane of the client satellite. The access time is also influenced by the inclination of the
client satellite, which would determine the relative velocities of the two satellites. The system is
simulated in MATLAB with the OuterNet at 900 km altitude and the client satellites at various
altitudes and inclinations. The resulting average access times are shown in Figure 4. The altitude
of 900 km was chosen in order to service a wide range of client satellites at altitudes ranging
from 300-800 km, while also keeping the aerodynamic drag force at a minimum. Less drag force
results in less orbital station keeping required and therefore less fuel required. Inter-satellite
communication can also be considered in the future to minimise the latency between client
satellites and a ground station. A message sent from a client satellite to the constellation could
then be relayed around the constellation to a constellation satellite that is above (or close to) a
ground station, allowing a message to reach earth within minutes.
10
2.5 Space Segment Description:
2.5.1 Link budget: A pointed VHF dipole antenna and a UHF patch antenna array will be used
to communicate with client satellites, while an omni-directional dipole will be used to
communicate with the ground station. Link budgets were calculated using the UHF downlink /
VHF uplink Full Duplex Transceiver as a worst case client transceiver. The transmitted power of
this module is only 150mW. Table 1 shows preliminary parameters of the link budgets with the
client satellite and with a ground station.
Table 1: Link Budget
2.5.2 For QPSK modulation Space Mission Analysis and Design:
The required OuterNet satellite antenna gains and required power were calculated using the
following link equation:
11
From this analysis it can be seen that the client downlink will require the most power and highest
satellite antenna gain, justifying the use of a patch antenna array. The antennas will have a beam
width of 60o per antenna spaced out by 22o, producing the pattern shown in Figure 5. Simulation
using STK showed that a client satellite with a 600km sun synchronous orbit, gave an average
access time of 60 seconds, allowing 35kb data per orbit to be transferred at 4800bps. A pass
through the constellations orbit without coverage happened 2 times in 41 passes, and never
sequentially. The range limitation was chosen to reduce LFS so that antenna gains would be
realizable, while still providing good coverage across the equator. The VHF losses proved to be
low enough to allow the use of a low gain dipole antenna. Communication between an OuterNet
satellite and a client satellite will be initiated with an ID, sent out by the nearest OuterNet
satellite. When the client receives its unique ID, communication between the OuterNet satellite
and client satellite will commence. The modulation technique and protocol of the communication
system on the OuterNet satellites will be software programmable, in order to accommodate as
many client satellites as possible.
2.5.3 Antenna Design: The key performance parameters identify the need for a lot of attention
to be given to the design of the antenna system. An antenna beam width of at least 150° in the
one direction and 60° in the other direction, as well as sufficient gain, need to be achieved. The
use of patch antennas will be preferred above other antennas due to their thin package form.
Different patch antennas for different frequencies can be stacked on top of one another to
minimise the area required [9]. Initial design points to the use of three patch antennas with a
relative angle to produce the 150° beam width. The VHF-band (145MHz) requires a very large
patch. Calculations show a patch of minimum length 0.32m, described by:
with 𝑐 the speed of light, 𝑓0 the resonance frequency, and 𝜀𝑟𝑒𝑓𝑓 the effective dielectric
constant [10]. Ceramic has an effective dielectric constant of 𝜀𝑒𝑓𝑓≈10. The antenna design
thus becomes unpractical. A dipole array will probably be used for the VHF-band and patch
antennas for the UHF and S-band. Consultation with experts on antenna design confirmed that
12
the antenna specifications are feasible with an antenna array. The final antenna design will be
shown in the final document.
Figure 2(d): Antenna coverage pattern
2.5.4 Attitude Determination and Control System: The satellites in the constellation will only
require pointing the S-band antennas to nadir. A control system is still required to de-tumble the
satellite after launch and to keep the satellite 3-axis stabilised at nadir pointing. The proposed
altitude of 900km is a bit far for gradient stabilisation and complete magnetic control. The initial
ADCS will make use of magnetic de-tumbling and reaction wheels to get 5° pointing accuracy.
The sensors to be used are a magnetometer, nadir- and coarse sun sensor combination for the
determination of attitude. This can be easily realised using existing off the shelf products to
reduce the required development time for these sensors.
2.5.5 Phasing: When the launcher reaches the desired orbit, all the satellites will be released at
roughly the same point in the orbit. To achieve the desired ≈25 degree spacing between each
satellite, cold gas (butane) thrusters system (Isp of ≈ 70) will need to be designed or bought and
intergrated to allow each satellite to enter and exit a phasing orbit. The satellite would need two
thruster burns: one at the start of phasing and one at the end of phasing. An example system
using this technique is SNAP-1 from SSTL [11]. The phasing of the satellites can confidently be
achieved with a cold-gas-thrusters system without adding too much complexity to the satellite
design. The thrusters will also allow for the capability to deorbit the satellite at end of life.
13
Chapter-3
WHAT IS CUBESAT?
3.1 Introduction: A CubeSat is a type of miniaturized satellite for space research that usually
has a volume of exactly one liter (10 cm cube), has a mass of no more than 1.33 kilograms and
typically uses commercial off-the-shelf components for its electronics.
Beginning in 1999, California Polytechnic State University (Cal Poly) and Stanford
University developed the CubeSat specifications to help universities worldwide to perform space
science and exploration.
While the bulk of development and launches comes from academia, several companies build
CubeSats such as large-satellite-maker Boeing, and several small companies. CubeSat projects
have even been the subject of Kick starter campaigns. The CubeSat format is also popular
with amateur radio satellite builders.
Figure3(a):- Cubesat
14
3.2 Design of Cubesat:
The CubeSat specification accomplishes several high-level goals. Simplification of the satellite's
infrastructure makes it possible to design and produce a workable satellite at low cost.
Encapsulation of the launcher–payload interface takes away the prohibitive amount of
managerial work that would previously be required for mating a piggyback satellite with its
launcher. Unification among payloads and launchers enables quick exchanges of payloads and
utilization of launch opportunities on short notice.
The term "CubeSat" was coined to denote nano-satellites that adhere to the standards described
in the CubeSat design specification. Cal Poly published the standard in an effort led by aerospace
engineering professor Jordi Puig-Suari. Bob Twiggs, of the Department of Aeronautics &
Astronautics at Stanford University, and currently a member of the space science faculty at
Morehead State University in Kentucky, has contributed to the CubeSat community. His efforts
have focused on CubeSats from educational institutions. The specification does not apply to
other cube-like nano-satellites such as the NASA "MEPSI" nano-satellite, which is slightly
larger than a CubeSat.
In 2004, with their relatively small size, CubeSats could each be made and launched for an
estimated $65,000–$80,000. This price tag, far lower than most satellite launches, has made
CubeSat a viable option for schools and universities across the world. Because of this, a large
number of universities and some companies and government organizations around the world are
developing CubeSats — between 40 and 50 universities in 2004, Cal Poly reported.
The standard 10×10×10 cm basic CubeSat is often called a "one unit" or "1U" CubeSat.
CubeSats are scalable along only one axis, by 1U increments. CubeSats such as a "2U" CubeSat
(20×10×10 cm) and a "3U" CubeSat (30×10×10 cm) have been both built and launched. In
recent years larger CubeSat platforms have been proposed such as 12U (24x24x36 cm) to extend
the capabilities of CubeSats beyond academic and technology validation applications and into
more complex science and defense goals.
15
Figure3(b):- Design of a Cubesat
Since CubeSats are all 10x10 cm (regardless of length) they can all be launched and deployed
using a common deployment system. CubeSats are typically launched and deployed from a
mechanism called a Poly-PicoSatellite Orbital Deployer (P-POD), also developed and built by
Cal Poly. P-PODs are mounted to a launch vehicle and carry CubeSats into orbit and deploy
them once the proper signal is received from the launch vehicle. P-PODs have deployed over
90% of all CubeSats launched to date (including un-successful launches), and 100% of all
CubeSats launched since 2006. The P-POD Mk III has capacity for three 1U CubeSats, or other
1U, 2U, or 3U CubeSats combination up to a maximum volume of 3U.
CubeSat forms a cost-effective independent means of getting a payload into orbit.[3] Most
CubeSats carry one or two scientific instruments as their primary mission payload. Several
companies and research institutes offer regular launch opportunities in clusters of several
cubes. ISC Kosmotras and Eurokot are two companies that offer such services.
16
3.2.1 System Design: The CubeSat program, created at Stanford University’s Space Systems
Development Laboratory, provides logistics and launch services for 1-kg cube-shaped satellites
measuring 10-cm on a side. CubeSats are deployed in groups of three from the Poly Picosatellite
Orbital Deployer (P-POD), designed at CalPoly-San Louis Obispo. Launch is aboard a Russian
Dnepr launch vehicle (converted from the SS-18 ballistic missile) from Baikonur Cosmodrome.
A generic CubeSat-based platform capable of satisfying the basic requirements of LEO-based
science missions was developed. This platform consists of all subsystems needed to support and
power a small science instrument as well as communicate data to a ground station. Additionally,
two separate science and attitude control subsystems were developed to accommodate the two
science missions.
3.2.2 Internal and External Configuration: Figure 3(c) depicts the internal configuration of the
CubeSat. The large toroid on the bottom face is the gravity gradient damper discussed in the
Attitude Control section below. The damper surrounds the tether deployer in this figure; the
boom mechanism used by the GPS mission also fits in this space. The communications, C&DH,
and science cards used by the CubeSat are arranged in a stack parallel to the bottom face, and the
batteries are enclosed in a separate box on the right side of the figure.
Figure 3(c)- Internal Configuration
17
Figure 3(d) is a series of diagrams outlining the spacecraft’s external configuration. The two
missions have slightly different external configuration needs. Common external components
include solar cells and a communications antenna, and both configurations provide access to an
RJ45 Ethernet port and a kill switch as specified by the CubeSat program. The DC/PIP mission
also incorporates two patch antennae for the science experiment, and the GPS mission includes a
pair of redundant GPS antennae. Both missions have equal solar cell coverage. All components,
with exception to the science packages, are off the shelf components and/or designed by the
students. The primary qualification of these components will be through thermal vacuum and
vibration testing on both the component and spacecraft level.
Figure 3(d)- External Configuration
3.3 Power Supply to a Cubesat: Satellites in orbit mostly derive their power from the sun. This
power is used to energize the satellite’s systems which include the payload and all of the
components that it needs to stay in orbit and function. Most satellites provide a very short
window of time for a controlling station on earth to manage its internal problems and for user
interaction with it. This is why the satellite needs to be an independent entity which can perform
its own housekeeping and its own fault corrections. This is especially true in the management of
power.
18
Systems in a satellite don’t exactly work at the same time and also an option is needed from a
user in an earth controlling station to be able to switch on or off these systems. Satellites in orbit
are exposed to radiation particles from the sun, this radiation in turn induce and produce faults
where a system drains too much power from its supply and overcurrent and overvoltage or other
power-related conditions take place. Also, satellites, apart from the energy received from the sun
need for a constant supply of energy when the satellite is on the shadow side of the earth where
solar energy collection is at a minimum so a battery pack works along with the solar collectors in
a way that the solar collectors can charge the battery while the batteries supply the system with
the needed power and when the satellite is in shadow the batteries work alone to give the systems
their needed power. From all of these requirements it is then known that it is necessary to have a
self-sustainable and smart power supply.
Eclipse Micropower Design’s project is to develop a smart power supply that can switch the
systems by itself either for necessity of use or because of a fault in the system. An On Board
computer takes charge of receiving data from sensing circuits and a microcontroller to then
switch on or off each individual system. As a future project proposal, this can also be done if a
user from an earth controlling station receives a report from the satellite that such action is
needed. Other options are available in the form of providing backup fuses for systems that use
them, such as the On Board computer. The system would then have to endure and be protected
from radiation in space, especially components having transistors and logic components and
ways of dissipating radiation or retain some for heating as would be in some cases were the
satellite, when in shadow is unable to keep a safe operating temperature for certain components.
The system will also be able to protect itself against temperatures by using circuits which
monitor temperatures in the various systems and are able to switch them on or off as needed.
19
3.4 Problem Definition: Most nanosatellite, picosatellite and cubesat missions fail due to
problems with their power supplies. A satellite needs to accomplish its mission with very little or
no human intervention and any overvoltage, undervoltage, overcurrent, undercurrent and
temperature fluctuation conditions can render a satellite’s systems useless. This is why a Smart
power supply option is needed where it is able to deliver power to the mission-required systems
and protect them should any problems arise. An intelligent power supply should be able to
extend the life of a satellite and all its components and guarantee mission success. The designed
system of the group is one such that it could be implemented by any client with a Cubesat
mission, regardless of its particular mission or power needs.
Some of the space environment variables that can affect a satellite’s system are:
1.) Temperature extremes: from -40°C to 80°C.
2.) Heat in the form of radiation, not convection or conduction.
3.) Radiation bombardment that can affect components by leaving “trails” of ionized particles
and cause short circuits. Also gamma rays and solar wind particles can induce overvoltage or
undercurrent conditions and damage systems.
3.5 Design Specifications: Eclipse Micropower’s Design solution for the Cubesat power
problem was to design a distribution system for the components of the Cubesat that monitors,
detects and corrects faults in voltage and current as well as providing temperature monitoring.
The group’s intent was to design a protection scheme for a Cubesat Power Supply Unit that
would be flexible, being able to be modified and used in any Cubesat mission or application.
In order to make a Power Supply Unit that is smart, operates with or without human intervention
and its capable of troubleshooting power issues on its own, the group has come up with a simple
scheme consisting of the following parts:
1. A 8.2V DC BUS connected directly to a 8.2V DC battery array which feeds system their
needed power.
20
2. A “slave” microcontroller which acts as a protection for the systems, to switch on or off the
systems as needed in the case of faults or simply by user demand and mission needs and provides
this data to the OBC which can be sent as reports to an earth control station.
3. A sensing/ switching circuit at the input of the systems that provides the Microcontroller with
voltage and current data. A current-to-voltage converter, (or transimpedance amplifier) is an
electrical device that takes an electric current as in
input signal and produces a corresponding voltage as an output signal. Three kinds of devices are
used in electronics: generators (having only outputs), converters (having inputs and outputs) and
loads (having only inputs). Most frequently, electronic devices use voltage as input/output
quantity, as it generally requires less power consumption than using current, as it is the case with
our Microcontroller.
4. DC/DC converters connected to the 8.2V DC BUS and to the input of the systems to provide
and control the operating voltages needed for the systems. A simple DC/DC power converter or
in electronics, a voltage divider (also known as a potential divider) is a simple linear circuit that
produces an output voltage (Vout) that is a fraction of its input voltage (Vin). Voltage division
refers to the partitioning of a voltage among the components of the divider.
The equation to calculate output voltage is given by:
Temperature sensing and switching of a warmer for batteries. Temperature sensors that would
monitor the system’s temperature, especially when the satellite is on the shadow side of the earth
and they can activate coil-based heaters to maintain the systems at normal operating
temperatures, especially the battery packs. They can also protect from overheating especially for
the batteries and Microcontroller.
21
Our design is one where each system in the Cubesat is monitored using a sensing circuit. The
Microcontroller has the minimum/maximum ratings of the system’s voltages and currents
programmed and if fed by the sensing circuit a parameter out of the predetermined values it can
make the decision and switch off the system and then later turn it back on after a set time.
3.6 Purpose of using a Cubesat: The primary mission of the CubeSat Program is to provide
access to space for small payloads. The primary responsibility of Cal Poly as a launch
coordinator is to ensure the safety of the CubeSats and protect the launch vehicle (LV), primary
payload, and other CubeSats. CubeSat developers should play an active role in ensuring the
safety and success of CubeSat missions by implementing good engineering practice, testing, and
verification of their systems. Failures of CubeSats, the P-POD, or interface hardware can damage
the LV or a primary payload and put the entire CubeSat Program in jeopardy. As part of the
CubeSat Community, all participants have an obligation to ensure safe operation of their systems
and to meet the design and testing requirements outlined in this document.
3.7 P-POD Interface: The Poly Picosatellite Orbital Deployer (P-POD) is Cal Poly’s
standardized CubeSat deployment system. It is capable of carrying three standard CubeSats and
serves as the interface between the CubeSats and LV. The P-POD is an aluminum, rectangular
box with a door and a spring mechanism. CubeSats slide along a series of rails during ejection
into orbit. CubeSats must be compatible with the P-POD to ensure safety and success of the
mission, by meeting the requirements outlined in this document. Additional unforeseen
compatibility issues will be addressed as they arise.
3.8 General Responsibilities:
1. CubeSats must not present any danger to neighboring CubeSats in the P-POD, the LV, or
primary payloads:
• All parts must remain attached to the CubeSats during launch, ejection and operation. No
additional space debris may be created.
• CubeSats must be designed to minimize jamming in the P-POD.
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• Absolutely no pyrotechnics are allowed inside the CubeSat.
2. NASA approved materials should be used whenever possible to prevent contamination of
other spacecraft during integration, testing, and launch.
3. The newest revision of the CubeSat Specification is always the official version
• Developers are responsible for being aware of changes.
• Changes will be made as infrequently as possible bearing launch provider requirements or
widespread safety concerns within the community.
• Cal Poly will send an update to the CubeSat mailing list upon any changes to the specification.
• CubeSats using an older version of the specification may be exempt from implementing
changes to the specification on a case-by-case basis. Cal Poly holds final approval of all CubeSat
designs. Any deviations from the specification must be approved by Cal Poly launch personnel.
Any CubeSat deemed a safety hazard by Cal Poly launch personnel may be pulled from the
launch.
3.9 Dimensional and Mass Requirements: CubeSats are cube shaped picosatellites with a
nominal length of 100 mm per side. Dimensions and features are outlined in the CubeSat
Specification Drawing. General features of all CubeSats are:
• Each single CubeSat may not exceed 1 kg mass.
• Center of mass must be within 2 cm of its geometric center.
• Double and triple configurations are possible. In this case allowable mass 2 kg or 3 kg
respectively. Only the dimensions in the Z axis change (227 mm for doubles and 340.5 mm for
triples). X and Y dimensions remain the same.
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Figure 3(e): CubeSat isometric drawing.
3.10 Structural Requirements: The structure of the CubeSat must be strong enough to survive
maximum loading defined in the testing requirements and cumulative loading of all required
tests and launch. The CubeSat structure must be compatible with the P-POD.
• Rails must be smooth and edges must be rounded to a minimum radius of 1 mm.
• At least 75% (85.125 mm of a possible 113.5mm) of the rail must be in contact with the P-POD
rails. 25% of the rails may be recessed and NO part of the rails may exceed the specification.
• All rails must be hard anodized to prevent cold-welding, reduce wear, and provide electrical
isolation between the CubeSats and the P-POD.
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• Separation springs must be included at designated contact points (Attachment 1). Spring
plungers are recommended. A custom separation system may be used, but must be approved by
Cal Poly launch personnel.
• The use of Aluminum 7075 or 6061-T6 is suggested for the main structure. If other materials
are used, the thermal expansion must be similar to that of Aluminum 7075-T73 (P-POD
material) and approved by Cal Poly launch personnel.
• Deployables must be constrained by the CubeSat. The P-POD rails and walls are
NOT to be used to constrain delpolyables.
3.11 Electrical Requirement: Electronic systems must be designed with the following safety
features.
• No electronics may be active during launch to prevent any electrical or RF interference with the
launch vehicle and primary payloads. CubeSats with rechargeable batteries must be fully
deactivated during launch or launch with discharged batteries.
• One deployment switch is required (two are recommended) for each CubeSat. The deployment
switch should be located at designated points (Attachment 1).
• Developers who wish to perform testing and battery charging after integration must provide
ground support equipment (GSE) that connects to the CubeSat through designated data ports
(Attachment 1).
• A remove before flight (RBF) pin is required to deactivate the CubeSats during integration
outside the P-POD. The pin will be removed once the CubeSats are placed inside the P-POD.
RBF pins must fit within the designated data ports (Attachment 1). RBF pins should not protrude
more than 6.5 mm from the rails when fully inserted.
3.12 Operational Requirements: CubeSats must meet certain requirements pertaining to
integration and operation to meet legal obligations and ensure safety of other CubeSats.
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• CubeSats with rechargeable batteries must have the capability to receive a transmitter shutdown
command, as per FCC regulation.
• To allow adequate separation of CubeSats, antennas may be deployed 15 minutes after ejection
from the P-POD (as detected by CubeSat deployment switches). Larger deployables such as
booms and solar panels may be deployed 30 minutes after ejection from the P-POD.
• CubeSats may enter low power transmit mode (LPTM) 15 minutes after ejection from the P-
POD. LPTM is defined as short, periodic beacons from the CubeSat. CubeSats may activate all
primary transmitters, or enter high power transmit mode (HPTM) 30 minutes after ejection from
the P-POD.
• Operators must obtain and provide documentation of proper licenses for use of frequencies. For
amateur frequency use, this requires proof of frequency coordination by the International
Amateur Radio Union (IARU).
• Developers must obtain and provide documentation of approval of an orbital debris mitigation
plan from the Federal Communications Commission (FCC).
• Cal Poly will conduct a minimum of one fit check in which developer hardware will be
inspected and integrated into the P-POD. A final fit check will be conducted prior to launch. The
CubeSat Acceptance Checklist (CAC) will be used to verify compliance of the specification
(Attachment 2). Additionally, periodic teleconferences, videoconferences, and progress reports
may be required.
3.13 Testing Requirements: Testing must be performed to meet all launch provider
requirements as well as any additional testing requirements deemed necessary to ensure the
safety of the CubeSats and the P-POD. All flight hardware will undergo qualification and
acceptance testing. The P-PODs will be tested in a similar fashion to ensure the safety and
workmanship before integration with CubeSats. At the very minimum, all CubeSats will undergo
the following tests.
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• Random vibration testing at a level higher than the published launch vehicle envelope outlined
in the MTP.
• Thermal vacuum bakeout to ensure proper outgassing of components. The test cycle and
duration will be outlined in the MTP.
• Visual inspection of the CubeSat and measurement of critical areas as per the CubeSat
Acceptance Checklist (CAC).
3.14 Qualification: All CubeSats must survive qualification testing as outlined in the Mission
Test Plan (MTP) for their specific launch. The MTP can be found on the CubeSat website.
Qualification testing will be performed at above launch levels at developer facilities. In some
circumstances, Cal Poly can assist developers in finding testing facilities or provide testing for
the developers. A fee may be associated with any tests performed by Cal Poly. CubeSats must
NOT be disassembled or modified after qualification testing. Additional testing will be required
if modifications or changes are made to the CubeSats after qualification.
3.15 Acceptance: After delivery and integration of the CubeSats, additional testing will be
performed with the integrated system. This test assures proper integration of the CubeSats into
the PPOD. Additionally, any unknown, harmful interactions between CubeSats may be
discovered during acceptance testing. Cal Poly will coordinate and perform acceptance testing.
No additional cost is associated with acceptance testing. After acceptance testing, developers
may perform diagnostics through the designated P-POD diagnostic ports, and visual inspection
of the system will be performed by Cal Poly launch personnel. The P-PODs will not be
deintegrated at this point. If a CubeSat failure is discovered, a decision to deintegrate the P-POD
will be made by the developers in that PPOD and Cal Poly based on safety concerns. The
developer is responsible for any additional testing required due to corrective modifications to
deintegrated CubeSats.
3.16 Future development: An example of one of the ELaNa satellites is the University of New
Mexico's Space Plug-and-play Architecture (SPA) proof of concept flight for the Trailblazer
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mission. Trailblazer is a 1U Cubesat to be launched in 2012 under the ELaNa four
mission. KickSat is scheduled for launch in early 2014.
The goal of the QB50 project is to use an international network of 50 CubeSats for multi-point,
in-situ measurements in the lower thermosphere (90–350 km) and re-entry research. QB50 is an
initiative of the Von Karman Institute and is funded by the European Union. Double-unit ("2-U")
CubeSats (10x10x20 cm) are foreseen, with one unit (the 'functional' unit) providing the usual
satellite functions and the other unit (the 'science' unit) accommodating a set of standardized
sensors for lower thermosphere and re-entry research. 35 CubeSats are envisaged to be provided
by universities in 19 European countries, 10 by universities in the US, 2 by universities in
Canada and 3 by Japanese universities. 10 double or triple CubeSats are foreseen to serve for in-
orbit technology demonstration of new space technologies. All 50 CubeSats will be launched
together on a single launch vehicle. The launch is planned for mid-2015. The Request for
Proposals (RFP) for the QB50 CubeSat was released on February 15, 2012.
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Chapter-4
CONCLUSION
Outernet is an ambitious project that seeks to create a global WI-FI network that would provide
the entire population of the world with free access to the Internet. A group of american
researchers is out to build a network of satelites that would provide Internet while at the same
time protecting the users identity and data. The new network is thought of as a new version of
short radiowaves or even a “space torrent”.
There are more WiFi devices in the world than people, yet only 40% of the global population has
access to the wealth of knowledge found on the Internet. The price of smartphones and tablets is
dropping year after year, but the price of data in many parts of the world continues to be
unaffordable for the majority of global citizens. In some places, such as rural areas and remote
regions, cell towers and Internet cables simply don’t exist. The primary objective of the Outernet
is to bridge this global information divide.
Offering continuously updated web content also bypasses censorship of the Internet in countries
that restrict access to independent media. Additionally, Outernet will offer a humanitarian
notification system during emergencies and two-way Internet-access for a small set of users. The
latter feature will be reserved for individuals and organizations that are unable to access
conventional communication networks due to natural disasters or man-made restrictions to the
free-flow of information.
Citizens from all over the world, through SMS and feature-phone apps, participate in building
the information priority list. Users of Outernet’s website also make suggestions for content to
broadcast; lack of an Internet connection should not prevent anyone from learning about current
events, trending topics, and innovative ideas. The project should start running simulations this
year, and in 2015 the initator want to start the construction phase.
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REFERENCES
[1] NASA. (2010, September) Tracking and Data Relay Satellites (TDRS). [Online].
http://nssdc.gsfc.nasa.gov/multi/tdrs.html
[2] CubeSatShop.com, CubeSat Summer Workshop at Small Sat Conference. [Online]
Http://www.cubesatshop.com/index.php?
page=shop.product_details&flypage=flypage.tpl&product_id=11&category_id=5&option=com_
virtuemart&Itemid=67
[3] Toorian, Armen et. Al, “CubeSats as Responsive Satellites,” Paper no. AIAA-RS3 2005-
3001, AIAA 3rd Responsive Space Conference, Los Angeles, CA, 25-28 April 2005
[4] CubeSat Kit (Pumpkin, Inc., San Francisco, CA). http://www.cubesatkit.com
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APENDIX-A
LIST OF FIGURE
FIGURE NO. FIGURE NAME PAGE NO.
1(a) Outernet Plan 4
2(a) Conceptual Illustration of Outernet 7
2(b) Interfacing Between System Segments 8
2(c) Antenna Coverage on Different Orbits 9
2(d) Antenna Coverage Pattern 13
3(a) Cubesat 14
3(b) Design of Cubesat 16
3(c) Internal Configuration 17
3(d) External Configuration 18
3(e) Cubesat Isometric Drawing 24
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